Climate Beyond the Greenhouse

Motl, Barton and the usual suspects make a lot of the fact that the Earth seems to have frequently been a lot warmer in the past than it is today. We are solidly in the territory of the colder periods of the Phanerozoic. This is not mainly an effect of CO2, though current CO2 levels seem to be low by the standards of 50 to 600 million years ago.

The biggest effect on climate (aside from the very slow warming of the Sun) is the position of the continents. Our current cold spell, during which we humans and much other life evolved, started when the Isthmus of Panama closed 5 Mya. If it opens again the effect on climate is likely to be as important as a couple or 3 CO2 doublings.

These things are well known to climate scientists, and don't affect their arguments (assuming the worst plausible feedbacks - methane clathrate melting) don't occur. Those who believe that anthropogenic CO2 will end the planet, or even the human race, are likely to be dissapointed.

It probably will suck to be Bangla Desh, a Pacific atoll, Florida, or Holland though.

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